1. Field of the Invention
This invention is in the field of water-blown foams and the method for production of such foams.
2. Description of the Prior Art
U.S. Pat. No. 5,010,116 describes a water-blown foam consisting of a mixture of polyether polyols, amine, organometallic and triazine/quaternary ammonium salt catalysts, surfactant, and 0.4%-4.0% water reacted with diphenylmethane diisocyanate. Although the density of the foam is not indicated, it would be expected that a free rise density of at least 1.8 lbs./ft..sup.3 would be obtained with a formulation containing 4.0% water.
U.S. Pat. No. 5,070,115 describes the process for producing a rigid foam from reacting an organic isocyanate with a mixture consisting of a polyester polyol with an OH value of at least 150, and/or a polyether polyol with an OH value of at least 200 which is combined with a polyether with an OH value less than 100. An NCO/OH ratio of 100-130 is used. The foam may have a density between 1.25 and 12.5 lbs./ft..sup.3 The examples cited use 4.0 parts of water and have densities ranging from 2.05 to 2.75 lbs./ft..sup.3
European Patent Application No. 450,197 A1 describes foam formulations suitable for preparing water-blown heat-insulating material using polyols as softening point improvers and heat-insulating material obtained therefrom.
European Patent Application No. 408,408 describes methods of producing rigid urethane foam by reacting blend polyol with polyisocyanate and water as blowing agent.
Because several fully halogenated hydrocarbons (chlorofluorocarbons, commonly referred to as CFC's) normally used as blowing agent are believed to cause environmental problems (for instance, their role in the deterioration of the stratospheric ozone layer), there is much effort in research for developing an alternative blowing agent that may (partly or wholly) replace the halogenated hydrocarbon as blowing agent in the standard foam formulations.
It was recognized that water, functioning as a reactant forming carbon dioxide (CO.sub.2) which acts as a chemical blowing agent, might replace the objected halogenated hydrocarbons. For example, European patent application published under No. 0,358,282 discloses foam formulations useful in the preparation of soft flexible polyurethane foam comprising water which is added as a replacement for chlorofluorocarbons. The reaction between the isocyanate and water produces carbon dioxide gas.